Super Smash Bros. 4 (also referred to by shorthands such as Smash 4 or SSB4) is an informal term used to refer to two games in the Super Smash Bros. series currently in development by Namco Bandai and Sora Ltd. The two games, entitled Super Smash Bros. for Nintendo 3DS and Super Smash Bros. for Wii U, will feature mostly identical gameplay, with some differences. The 3DS version is the first game of the series to be released on a handheld.

When originally announced in passing at E3 2011, the game's development was slated to begin sometime after October 2011, once development on Kid Icarus: Uprising had completed. In February 2012, it was then confirmed that development on the fourth game had begun. The game was unmentioned during E3 2012, something which many fans were disappointed about despite the known extremely early state of the game; the "first step of the process" was taken shortly after in mid-June. Masahiro Sakurai has expressed disappointment that fans will be waiting for longer than expected for the game to be released due to the earliness of the initial announcement. Shortly afterward, it was revealed during a Nintendo Direct that Namco Bandai was the primary developer alongside Sora Ltd., and had already completed a working prototype.

The paired versions of the game were officially revealed at E3 2013 in the form of a trailer on June 11, 2013. The 3DS version is scheduled to launch in Japan on September 13, 2014 and in most other parts of the world on October 3, 2014. The 3DS version will be released in stores one day earlier in Germany on October 2 in order to avoid coinciding with a national holiday, and one day later in Australia on October 4. The Wii U version will be released in the holiday/winter season of 2014.